Formation of phalanges and small joints by tissue-engineering

Background: This report describes the formation of small phalanges and whol e joints from three types of bovine-cell sources transplanted onto biodegra dable polymer matrices. The resulting structures had the shape and composit ion of human phalanges with joints, Methods: Fresh bovine periosteum was wrapped around a copolymer of polyglyc olic and poly-L-lactic acid. Separate sheets of polyglycolic acid polymer w ere then seeded with chondrocytes and tenocytes isolated from the shoulders of freshly killed calves. The gross form of a composite tissue structure w as constituted in vitro by assembling the parts and suturing them to create models of a distal phalanx, a middle phalanx, and a distal interphalangeal joint, Results: Subcutaneous implantation of the sutured composite tissues into at hymic mice resulted in the formation, after twenty weeks, of new tissue nif h the shape and dimensions of human phalanges with joints. Histological exa mination revealed mature articular cartilage and subchondral bone with a te nocapsule that had a structure similar to that of human phalanges and joint s. There was continuous cell differentiation at the ectopic site even after extended periods, Conclusions: These findings suggest that the formation of phalanges and sma ll joints is possible with the selective placement of periosteum, chondrocy tes, and tenocytes into a biodegradable synthetic polymer scaffold. Clinical Relevance: The formation of a joint construct of this nature is an example of a growing list of tissue-engineering techniques that, in genera l, offer alternatives to obtaining autogenous tissue for reconstructive ope rations in humans, Tissue-engineering holds promise for the treatment of lo ss of tissue or organ function as well as congenital malformations. Difficu lt reconstructions in symphalangism, arthrogryposis multiplex congenita, br achydactyly, or traumatically fixed joint contractures may someday be perfo rmed with this approach.